Two Honda motorbikes have become the latest victims of mysterious fires that have burned more than 90 vehicles across Vietnam since last year.

One of the new cases happened in the central province of Thua Thien Hue right after Hoang Thi Mai Tram left Hue Central Hospital, where she works, on Thursday.

Tram said she found a fire burning below her motorbike's storage compartment, so she stopped it and used a bottle of saline solution to put it out.

According to Tram, after the fire, she checked her bike and found that some of the electrical wires had been burned.

That same day an Air Blade also caught fire in the northern province of Bac Ninh, when Thang Thi Thu Phuong, 33, had just arrived at Dong Nguyen Secondary School for a parent meeting.

Phuong said she saw smoke coming from the rear of her motorbike and the fire was extinguished quickly without causing major damage, thanks to locals.

A report on VnExpress Friday said the Directorate for Standards, Metrology and Quality has taken gasoline samples from Phuong's bike to be tested, given that poor-quality gasoline is being considered as a possible cause of vehicular fires.

However, Tran Van Vinh, deputy chief of the directorate, was quoted as saying checks on the bike at a local Honda agent found that the fire likely occurred due to rats chewing through the motorbike's fuel pipe, allowing gasoline to leak and ignite.

He said large-scale inspections are needed in the future to clarify the root of fires that damaged or ruined 89 vehicles last year and at least five this year. The official also suggested people and related agencies should cooperate with the directorate to solve the cases, more than 50 percent of which remain unexplained.

At the moment, poor-quality gasoline mixed with additives to increase its combustion is under suspicion, as experts argued that the additives like methanol can erode rubber materials, allowing fuel to leak and ignite.

However, samples taken at several gasoline stations where the owners of burned vehicles bought fuel before the accidents have passed all tests administered by the directorate so far, VnExpress reported.